(a) Field of the invention
The present invention relates to a waste water and sewage treatment system for use in an aeration-sedimentation basin or lagoon.
(b) Brief description of the prior art
A conventional method of treating industrial or municipal waste water and/or sewage consists in subjecting them to an aerobic digestion into one or more basins or lagoons. For the purpose of simplifying the following description, only the word "basins" will be used hereinafter to identify both the basins and lagoons.
To achieve such an aerobic digestion, the waste water or sewage is subjected in the basin to an aeration treatment that is usually carried out by mere injection of oxygen or air into the waste water. Such an injection can be carried by means of jets-aspirators each consisting of a water jet incorporating an air sucking venturi making it capable to draw in atmospheric air and blow it into the waste water or sewage to be treated.
From time to time, it is of course compulsory to remove the sludge which settles and accumulates at the bottom of the basin. To do so, it is of common practice to scrap the bottom of the basin with a drag line or with a bulldozer. In the latter case, the basin must of course be emptied. In both cases any way, the sludge removal is time consuming and very expensive operation.